I'm working on a system hand off nodejs workloads over a serial port to another machine running some host software.
My intent is to easily write Internet-connected software for old machines where a host machine is doing all of the heavy lifting. I have been messing with 68k Macintosh systems first. The code is very much a work in progress that I am actively chipping away at, and not in a usable state just yet. I write a lot of nodejs professionally but haven't used C since college so its been a fun project.
nodejs software for the "modern" machine: https://github.com/CamHenlin/coprocessor.js
C software (targeted at a 68k mac) for the "slow" machine: https://github.com/CamHenlin/retro68-coprocessorjs-test